Automatic telephone trunking system



w. E. LAMB.l UTOMAUC TELEPHONE TRUNKING S ,YS`I"EM'.F

v r l APPLICATION FILE/D SEPT. l, 191|.

Patented Aug.' 1, 1916. 2 SHEETS-SHEET' l W. E. LAMB.

AUTOMATIC TELEPHONE TRUNKING SYSTEM.

APPLICATION yFILED SEPT- l.' 19H1 1 9 1 93,1 60, Patened Aug. 1, 1916.

2 'SHEETS-sain 2.

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XVILLISE LAMB, OF CHICAGO. ILLINOIS, ASSIGNOR TO! AUTOMATIC ELECTRIC COMPANY, OF CHICAGO` ILLINOIS, CORPORATION OF ILLINOIS.

AUTOMATIC TELEPHONE TRUNKING SYSTEM.

Specification otgL-etters Patent.

l latented Aug. 1, 1916.

Application filed Septenibc'i-ll, 1911. Serial No. 647,146.

Be it known that I, rinus 1C, Lamu, a citizen of the United States of IHOICII, and resident of Chicago, Cook county, Illinois, have invented Certain new and useful Improvements in' Automatic 'ilelcphone Trunking Systems, of which the following is a specification.

My invention relates to autoi'natic or semiautomatie telephone systems, and more partieularly to an improvedconstruction in a non-numerical trunking switch for. use in such a system. i

My invention is in the nature. of an im rrovement upon the non-numerical trunkiug switch described in the application of? F. J. Truhy for improvement in automatic trunking systems, Serial No. (303,303, filed .Tannary 18, 1911, in thatl it relates to a rotary non-numerical switch the wipers of which rotate in `but one direction and do not return to normal posit-ion. Then a connection involving the line switch is'released, the wipers remain resting:r upon the contacts otft-he trunk over which the connection was estalilished, hutthe' line is disconnected from the wipers. 1f this trunk line is idle-when the next call is made through this switch, the line simply becomes connee `;ed with the wipers, the wipers themselves remaining stationary. 1f the trunk upon which the wipers are resting is busy when a. call is made, the switch automatically rotates to an idle trunk hefore the line is cut tlirougliito the wiper?. My line switch is an improvement over the line switch of Truhy, referred to above, in that it is simpler and requires fewer relays. This simplification is obtained by arranging a Single relay so thatl it may perform both .the duties of a. cut-off relay to cut oil' the linerelay, and a liner-switchingrelay to connect the line with the wipers. This cut-off relay is so arranged that it is Acapable of cutting off the line relay when the line to which the switch belongs is either eallinlg` or is calli-il, while it operates as a line-switching relay 'to cut the line through to the wipers only when the line is calling.

These and other objects of my invention will he more clearly understood by reference to the accompanying drawings, in which I A' in a system einbodyingthe principles of I my invention. Fig. 3 vis adiagrairimatic representation of the essential parts of the suhscrihers individual switch C (Fig. 1).

rflic connection represented in Figs '1 and 2 is established through the medium of a subscribers individual or Lline switch C,

lhrst selector D, second selector E and connector F. The lgeneral character of automat-ie exchanges employing line switelies'seleetors and connectors are w ll known in the art and will not` be explained-iii detail;

herein.

'llie'si'ibsr-.ribers Suhstations A and vmayv he of any suitable chain-eten.

As herein shown, the substation A comprises' the usual 'receiver 2,. transmitter; Si, switch iioolr. 4-,

ringer 5 and condenser (3. .Being'anautomatic substation, it is alsoproi'ided with au automatic calling device comprisiupr a pair 'of interruptor springs 7 and S and a toothed impulse wheel 9. rlhe impulse wheel Slis Vsecured to a shaft 10 t.; which there. is also attacliel a dial (not shown) provided with linger YiolPS. 1n order to call au)Y iliit, the calling` subscriber rotates thi` dial through the medium ofthe finger holes and then allowsA it to return to normal position. Dui*- ing the return motion the impulse wheel S) separates the .springs 7 and S a number of times. ':orresponding to the digit called. y

The suhscriheis individual switch C comprises a set of wipers 11, 12 and 153 carried upon a suitable rotary shaft (not shown iu Fig l) which. is controlled by a motor magfnet 14. The wipers 11, 12 and 1? are adapted to rotatiorer and make connection with l'iaulis of contacts which form the terminals of trunk lines leading to the selectors D. The line switch C is of the nou-releasing typc-that is., the wipers never return to noi'iiial positiozuliut. always4 rotate iii the same direction. The haul: couiaris unir lu- `armature is completely retracted.

arranged to form a complete circle around the shaft of the switch, or they may form only at. portion of a circle, and the wipersmay-each be provided with a plurality of arms so arranged that as one arm passes off the last contactthe nextarm will engage the first contact. This latter arrangement is shown in Fig. 3, wherein one Wiper is shown having three arms 15, 1G and 17. These arms are adapted to engage a bank of contacts containing ten individual segments a, and are so arranged that as the arm 15 passes off the last segment the arm 17 engages the first one. In order to avoid the use of wiper cords for connecting the subscribers lines With the wipers, the banks are made to comprise a common segment 18 situated below. and insulated from the individual segments a. The wipers may then be simply shortcircuiting wipers, so as to connect the common segment 18 with the particular individual contact on which the Wipers are resting. For simplicity, the lines are shown connected directly with the wipers in Fig. 1. The motoll magnet 14 is provided with means for interrupting its own circuit. A number of means are in use for this purpose, but l lind that shown in Fig. 3 to give better results than any others. This interrupting means comprises a pair of springs 19 and 20 which are separated by the bushing op the end of the arm 21, which latter is attached to the armature of the magnet. This arm is so adjusted that it separates the springs 1i) and 20 just as the armature reaches the conr pletie I of its stroke. These springs are,

thereore, closed 'very shortly after the armature begins its return stroke, so that the magnet begins to be energized before the This allows a very rapid operation of the line switch, and makes it possible for the Wipers to be rotated over the contacts at a rate of about thirty per second. Also governed by the arm 21 there is a spring 2Q which is normally held out of engagement with the spring 20, but which is permitted to engage thespring 20 before the spring 19 is separated therefrom when the magnet 14 is energized. The switch C is also provided with a line relay 24 and a cut-oli' relay 23, the line relay 24 being connected to the subscribers line through contacts controlled by said cut-olf relay.A These relays are interlockingthat is, in normal position the armature of the relay 24 overlaps the end of the i armature of the relay 23, so that if the relay 23 iS energized while the relay 24 is in nor- ,mal position, the armature of the relay 23 cannot be pulled all the way up. It can be pulled `up far enough, however, to separate all of the springs of the relay from their 'back contacts, but not far enough to close the front contacts.

The tirstselector D is of the general type shown in United States Letters Patent No. 815,321, granted March 12S, 1906, to Keith, Erickson Erickson, being modified, however,in order to operate in a socalle twr wire system--that is, a system in which the central ollice apparatus is controlled over the two sides of the calling line in series. lt comprises among other details a set of wipers 25, 213 and 2T carried upon a shaft (not shown) which has a vertiral motion controlled by the .so-called vertical magnet 2S and a rotary motion controlled by the rotary magnet 2). The usual side switch comprising the wipers 31 and "2 is controlled by the private magnet 33 in a wellknown manner. The usual release magnet 34 yis provided for restoring the switch to normal position. This release magnet, however, restores the switch immediately upon energization as shown in United States Letters lalent No. 815,176, granted March 13, 190V, to Keith, Erickson E Erickson for connector switches, instead of upon denergization as shown in said selector patent.. The springs 235 and 3G which are included in the release magnet circuit are permitted to close only when the switch shaft is raised one or more steps from its lowest position. The relays 4 and 3S are slow acting relays-thatis slow to denergize when their circuits are broken. The dnublewourui line relay is connected with the line through the springs ot' the line-suitching relay il). In said selector Patent No. 815,321 the ro tarymagnet armature controls the armature of the private magnet mechanically. In the selector D Shown herein, however, the rotary magnet controls the private magnet electrically through the medium ot' the contact 41. The second selector E is essentially the same as the first selector l). The connector l" (Fig. is of the general type of con- Hector switches shown in said connector atent No. 815,176, being modified, however, like the selector switches, in order to oper` ate in a two-Wire system. Associated with th'e connector there are shown a ringing current generator H and a busy signaling device L.

The called substation A and its line switch C are in all respects the same as the substation A and the line switch C (Fig. 1.).

1n order to give a clearer understanding of the invention, l will describe in detail how the subscriber at substation A may ol`- tain connection with the subscriber at substation A, the number of which latter will be assumed to be 2220. ln the system shown herein, the subscribers lines are divided into" groups, and the individual Iswitcllies C of all the lines belonging to the same group have Y common access to the same group of first se- 4line with the wipers.

dividual switches of the group. As has been explained, the individual switches (i shown herein do not release and return to normal position upon the termination of the connection. These switches have no normal position, their. Wipers normally remaining in Contact with the trunk line which was last used by the switch. Therefore, it will be seen that when' the subscriber' at substation A Iinitiates a call, the wipers of the switch C may be standing upon' the contacts of either a busy trunk or of an idle trunk. It thc wipers are standing upon the contacts of an idle trunk, the Wipers do not rotate when the subscriber at substation A makes a call, but the relay 23 simply operates to connect the It the trunk upon which the wipers are standingwhen the sub scribe-r at substation A makes ajcall is busy, the Wipers are rotated to an idle trunk before the line is connected with them.

When thesubscriber at substation A re moves his receiver preparatory to making a call, the engagement of the vhook switch springs 42 and 43 closes a circuit through the line relay 24 of the switch C, said circuit extending from ground G through the springs 44 and 45, line 53, springs 42 and 43, l8 and '7, receiver 2, transmitter 3, line 54, springs 48 and 47 and the relay 24 to the battery lead 55, thence through battery B to ground G. The relay 24, upon energizing, completes a circuit extending from ground G2 through the springs 56, relay 28, interrupter springs 20 and 19 and the motor magnet 14 to the battery lead 55. If the wipers of the switch C are standing upon an idle trunk, the c losure of this circuit causes the relay 23 to be energized, but the relay 23 being of a coinparatively high resistance does not permit suiiicient current to flow through the magnet 14 to cause it to be operated. 1t', however, the wipers of the switch C are standing upon the contacts of a busy trunk line, the. wiper 12 Will be Standing upon a contact which is grounded. Therefore, when the relay 24 energizes, the relay 23 `will not be energized, because it will be short-circuited over a circuit extending from the grounded private bank contact upon which the wiper12 is resting, thence through said Wiper', springs 51 a nd 50, springs 57 of the relay 24, thence through the relay 23 and springs 5b ot' the relay 24 to ground G2. The short-circuiting of the rclay 23 not only prevents it from energizing, butvalso causes the motor magnet 1i to be operatively energized. The magnet 14 will, i refore, attract its armature to advancethe wipers of the switch one step and to interrupt its own circuit at the springs 19 and 20. If the next trunk is busy'also, thc wiper lz will find the next Contact grouudcd, ulrich Will cause the motor magnet 14 to oc cncrgized again to rotate the wipcrs anothcr stcp as soon as the interruptcr springs li and lil come into contact. In other words, the motor magnet 14 continues to operate in a man 4ner similar .to that of a buzzer to rotate the 'busy trunks. As soon as the wiper 1:31

reaches the non-grouruled Contact of an idle trunk, the relay 2?, ceases to bc short-circuited and becomes operatively energized over the circuit traced above, W'heii thc relay 23 encrgizcs. the shitting of the springs 45 and 48 disconnects ground G and the .line relay 24 from the calling line, and extends the .line connection through the wipers 11 and 13 to a first selector l);

lVhen the connection is extended to the iirst selector, its linc relay 3S) becomes encrgized over a circuit extending from ground (,1 through the lower windingr of said relay, springs 5S and 535), wiper 13, springs 4G mid 45, thence to and through the sub-station A and back over the other side oi thc line through the wiper 11 of thc switch C, springs (30 and (31 and the upper winding of the relay 39 to theI battery lead. The relay' 3i), upon energizing, completes a. circuit cxtcndingtrom ground G* through thc spring (32 and its front contact and the relay 87 to thebattery lead. The relay 37, upon energizing, extends a guarding potential from ground G through thel springsl G3 to the private bank contacts of tbc trunk leading to the selector l) in all of' the individual switches which have access to said trunk. The wiper 12 being in contact with the private bank contact ot' this trunk, a circuit also extcnds through the springs 51 and 52 and through the relay 23 and magnet 14 to battery. 'l`l1c1'cfo1'c,'tlic cnergization of the relay :11T at the selector l) provides a holding circuit l'or the relay 23 to prevent it from being,v dciiocrgized when its circuit is broken by thc liuc relay 24 after it is disconnectcd trom the line. The engagement of the springs (iii at the selector l) also extends a guarding potential back through the switch C and over the conductor (34 to the connector private bank contacts of the calling line. lt will be seen that while the motor ma"- n nct 14 olf thc lmc switch C operating to rotate the wipers in search of an idle trunk, thc sprino 2; engages the spring 2() before thc spring 2() is separated tronrthe spring 1S). Thcrctorc` just bcforc thc springs lil and 2() aac finally scparatcd, thc magnet li is not being energized alouc by thc ground supplicd from thc guarded private bank contacts through thc 'ipcr 12, but also rcccivcs curl'cnt through thc ground conucc iion (i'VI and thc spring 22. ly this arrangcmcut, when thc wipcr l2 passes oli llic last grounded contact. there is no circuit inicrruptcd at said wipcx' and thcrclorc thcrc is no sprrk to burn thc contacts. ll. il wcrc not l'or thc provision ol` thc spring' vmagnet 33 to battery.

22 on the motor magnet, it will be evident that if the wiper 12 left the last grounded contact before the springs 19 and 20 were separated, the operating circuit of the magfnet 14 would be broken at the private wiper. This would not only tend to prevent the magnet 14 from completely'energizing, but would also cause a spark between the private wiper and its bank contacts, which, since they were not supplied with platinum contacts, would be very objectionable. The line relay of the switch C is slow acting, so that it will not denergize and break the circuit of the switching relay 23 until after the relay 37 at the selector .D has had time to complete the holding circuit for said relay 3.

The foregoing operations take place immediately upon the removal of the receiver at the calling telephone and before the calling device is operated for the first digit. Vhen the calling device is operated for the first digit 2, the impulse springs 7 and S are momentarily separated twice, each time causing the line relay 39 of the selector D to be de'energized momentarily. The relay 37, being slow acting, does not have time to deenergize during the momentary interruption of its circuit by the relay 39, and therefore each time the relay 39 denergizes, a circuit is closed from ground Gtthrough the spring G2 and its back contact, spring G5 and its front contact, relay 38, vertical magnet 2S and side switch wiper 31 to battery lead The digit called being 2, the vertical magnet receives two impulses over this circuit and operates to raise the switch shaft and wipers two steps. The relay 38, which is included in the circuit of the vertical magnet, is energized by the first impulse, but, being a slow acting relay, does not de energize untilafter the last impulse is delivered. In its energized position, the relay 38 completes an energizing circuit for the private magnet 33. This circuit is, of course, broken when the relay 38 denergizes after the last impulse is delivered to the vertical magnet, and the private magnet 33 in turn denergizes and permits the side switch to pass to second position.

lV hen the side switch wiper 31 engages its second-position contact point, a circuit is closed from ground GG through the interrupter springs (5G, rotary magnet 29 and side switch wiper 31 to battery.. The rotary magnet thereupon begins to operate in a manner similar to that of a buzzer to rotate the wipers step by step in search of an idle trunk line. As soon as the rotary magnet energizes the first time, a circuit is closed from ground (iC through the contact 41 and private- 1f the first trunk line upon which the wipers of the Vselector are rotated is idle, this impulse through the private magnet causes the side switch to be tripped to third position, thereby completing connection with this trunk line. 1f this first trunk the private wiper 26 finds the contact which it engages provided with a guarding ground poteiitial, whereby a locking circuit is completed from said grounded bank contact through the wiper 2G, side switch wiper 32 (in second position) and private magnet 33 to battery. The closure of this holding circuit through the private magnet prevents the private magnet from denergizing when the contact Li1 is opened, and thereby causes the side switch to be locked in second position, and the rotary magnet continues to ad vance the wipers step by step untii an idle trunk is found. `When the wiper 2C leaves the contact of the last busy trunk, the hold* ing circuit of -the private magnet is broken and the side switch passes to third position. The movement of the side switch wiper 31 from second to A operating circuit of the motor magnet and closes the circuit of the imc-switching relay 40. This circuit extends from ground G through the spring 63, relay 40 and side switch wiper 31 to battery. The relay upon energizing, disconnects theiine re i from the line and extends the conm-cuorl over the heavy conductors through the wipers 2T and 25 tothe second selector be line relay 68 of the second selector thereupon becomesenergized in the same manner as explained for the line relay 39 the selector D, The relay GS, upon energizing, closes the circuit of the relay G9, which corresponds with the relay 37 of thev first selector D. The relay 69, upon energizing, extends a holding circuit from ground G7 through the springs 70, private Wiper 26 of the selector D, side switch wiper 32, relay fi@ and side switch wiper 31 to atte-ry. The closure of this circuit maintains the rela'v 4l) 4energized after .i circuit is broken by the deenergization of the relay 37, which takes, place shortiy after disconnected from the line and aiiowed to dene-rgize. The closure of the springs 70 ot the reiay 69 of the selector E also provides a guarding potential theI selector private bank contacts of the trunk leading to the selector E, and also substitutes ground G7 for ground G conductors and 73 to a connect-or i? line is busy, however,l

third position breaks the l at the` selector D in the holding circuit of the line its original energizing EEG ough the rel; y

tmf-wl mm Thx 'tion was.

viv

V.. menti gli;

trunk, whether this trunk extends to an automat-ic switch' or to an operators position.

lVhat I claim as my invention iszsl. In a telephone system, a subscribers line, trunk lines, a trunlcing,r Switch for said snbscribers line. for selecting an idle trunk, the wipers of said switch normally engaginer one of said trunk lines, a line relay normally connectedhvith said line, a cut-oil' relay, means controlled by said eut-olf relay for cutting;r ofl' said line. relay from the line when said subscribes line is either callingIf or being called, means controlled by said cnt-off relay for connecting said line with one of said trunks when said line iscalling, and means including an automatic switch for extending a connection to the called line. .l

2. I n a. telephone system, a subscribers line, a non-numerical trunking switch therefor, Vtrunk lines for talking purposes, said switch including line wipers always in electrical engagement with one of said trunk lines, a relay in 'said switch, a cutoll` relay, means controlled by said cutoff.

relay for openingr the circuit of said firstrnent-ioned relay when said line is calling or being'called, and means Controlled b v said cutfolf relay for connect-ing said linc wipers vwith said subseribers line.

3. ln a tclephoneesystem, a subscriberis line, a non-numerical trunking,r switch therefor, trunk linesfor talking purposes, 'said switch including,r line wipers always in electrical engagement withl one of said trunk lines, a line relay in said switch normally connected with the subscribers line, a cntlotl relay, means controlled by relay for cutting off said line relay Vwhen Said line is calling or being called, and means' controlled by said cut-off relay for connect-ing;` said line wipers with said subscribers line.-

4 ln a telephone system, a non-numerical trunking switch, trunk lines for talking, purposes leading therefrom, said switch in cluding,r line wipers always in electrical engagement with one of said trunk lines, a slow actingr line. relay for controlling the operation of said switch, a cnt-Oli' relay, means controlled 'by said eut-off relay for opening the circuit of said line relay, and means'controlled by said line relay for contnolling the externgAof operation of said cnt 5. In a telephone system, a non-numerical trunking switch, trunk lines for talking,r purposes leading therefrom, a line. relay controlling the operation of said"switch, a cut-off relay for controlliny the circuit of said line relay, and means controlled by said line relay for mechzmicallj,v controlling' the extent of operation of said cnt-ol relay.

( i. In a telephone system, a non-numerical contact.s, but -is permitted said cnt-oli trnnking vswitch,'trunk lines for talking purposes leadingv therefroi'n, sa id switch har'- irrer line wipers always in electrical engagement with one ot' said trunk lines` a line relay controlling' the operation of said switch. a cnt-ofi relay, means controlled by said cnt-oil' relay for said line relayt and for extending connection to said trunk lines, and means` controlled hr said line relay for mechanically contr-filling the extent of' operation of said cnt-oli' relay.

T. ln a telephone system, a mmmmner'ical trunking,r switch. trunk lines for talking purposes extendingt therefrom, a. lineVv relay controlling the operation of said switch, a cut-olf relay controlling the-circuitof said line relay, and'means'controlled by said line relay for mechanically contrr'rlling the -extent of operation of said cut-off relay.

opening.;r the circuit of hai-ingsY both trontrand back cont-acts` and l means controlled by said line relay whereby in normal orA delinergized l olf relay prevented from to Alopen its bajek contacts. i l

S). In a telephone systenna non-numerical trunking switch, trunk lines -for .talking purposes leading therefrom, saidvswitcli havl mg line wipers always in electr-ical engagement with some one of said trunk-lines, a line rela?,r for controlling the'` operation of said switch, a cut-oli relay havinf both iront a nd back contacts,- ineanscontrolled by sa id lino relay whereby when. Isa-iddine relay.

is denergized said `cut-olf relay to open its bark contacts to open the circuit of said line rel'ayfbut is prevent-cd from closing its front, contacts to extend -connection to said trunk line.

l0. ln a telephone systen'i, a line switch, a line relay therefor, and a switching,r relay forcnttingwtf the vline relay and closingthe line thronclrthe switch` said switching relay living operative to perform both its functl-ons when the\liiie is calling, but being,r operative to cut all the line'relay and inoper? atire toclose tlie line through when the line is called. i

l1. ln a telephone system. a line switch, a line relay therefor, a cutoff relay` said cut:

is adapted oft relay being operative to 'cutoff the linerelay and Vclose the whereby the second relay when in normal or deenergized, position renders the first-mentioned relay inoperative to close its front contacts, but pefniits it to open its back contacts.

i3, in a telephone system, a snhscrihers line, troni; lines, a trunking switch for said subscriners line for selecting an idle trunk, a slow-acting line relay normally connected with said line, a cut-oil' relay, means con trolled by said "cut-olf relay for cuttingr oli' said line relay `from the line when said sulsoribers line is either calling or being called, and means controlled by said cut-ott relay for connecting saidA line with one of said trunks when said line is calling.

i4. in a telephone system, a subscribers line, trunk lines, a trunking switch for said subscriber-s line, a line relay normally connected with said line, an operating magnet controlled by said line relay, a cut-oil' relay, a test conductor for each trunk` automatic means for applying a potential to said test conductor, said operating magnet being respons-ire to said potential to move saidI switch progressively over saidv trunks until a trunk is found withoutsuch potential on its test conduct-or, means cont-rolled 'oy said cutoff relay for cutting otf said line relay from the line when said subscriber-s line is either calling or being called, means con vtrolled bv said o ieratinff inaffnet for diu I-l L9 rectly controlling the circuit of said eutoft relay, and means controlled by said cutoff relay 'for connecting said linel with one of said trunks when 'said line is calling.

15. In ateleplione system, 'a subscrihers line, trunk lines, a trunking switch for said subscribers line for selecting an idle trunk, a line relay normally connected with said line, a cut-ofi' relay, means controlled by said cut-oit' relay for cutting oi said line relay from the line. when said suhsoi'ibcrs line is either calling or being called, means controlled by said cut-oil relay for connecting,r said line with one of said trunks when said line is calling,vand a short-circuit for said cutoii' relay controlled by said line relay to prevent the operation of said cut-olf relay when a lousy line is found,

lf3. ln a telephone system, a nonfnuineiical trunking switch, trunk lines for talking: purposes extending therefrom. a line relay cont-rolling the operationk of said switch, a cut-ott' relay controllin; r the circuit ot said line relay, means controlled by said line relay for mechanically controlling the extent ot operation ot' said cut-oil' relay, and wipers for said switch normally engaging one oi" trunk lines.

17. in a telephone system, a non-nui nierical triniking,r switch, a line relay for" controilinfij the operation of said switch, a zutfol'l relay having hot-h front and back contacts, ine-ans controlled hy said line relay whereby in normal or denergized positionl the cutoff relay is prevented from closing its front contacts, but is permitted to open its back contacts, and wipers for said switch 'normally engaging one of said trunk lines.

1,8, ln a telephone system, a line switch, a line relay therefor, a switching relay for cutting off the line relay and closing tne line through the switch, said switching relay being operative to perform both its functions when the line is calling, but being operative to cut off the line relay and inoperative to lay and inoperative to close the linel through if it is energized while the line relayv is deinergized, and wipers for said switch normally engaging one of said trunk lines.

20. lu a telephone system, a suhscribers liuc, trunk lines, a trunking switch for Said suliscriliers liuc, a line relay normally connected with said line, an operating magnet controlled by said line relay, a cut-oil relay, means controlled hy said cut-oll relay for cutting oilA said line relay from the line when said suliscrihcfs linc is either calling or being called, means controlled by said operating magnet for directly controlling the circuit of said cut-oil' relay, means controlled by said cut-off relay for connecting said line with one of said trunks when said line is calling, the wipers of said switch normally engaging one of said trunk lines.-

;21. ln atelephone system, a subscrihers line, trunk lines, a trunking switch `for said subscrihers line tor selecting an idle trunk, the wipers of said switch normallycngaging A one of said trunk lines, a line relay normally connected with said line, automatic means for progressively moving said switch unon cnergization of the line relay, autonatic means for stopping said switch without further action on the part of the line relay, a cut-ott' lay, means controlled by said cutoll' relay for' cutting oit said line relay om the line when said subscribers line is either calling or heilig called, and means controlled oy said cut-off relay. for connecting said linc with one of said trunks when said line is calling. v

22. In, a telephone system, -a subscribers line, a non-numerical trunking switch therefor, trunk lines for talking,r purposes, said switch including line wipers always in electrical engagement with one of said trunk lines, a relay in saidmy'itcli, automatic means for progressively moving said lswitch upon the energization oi thc relay, automatic means for stopping said switch without further action on 'the part of the relay, a (Jut-oli iclay.r maar controlled by said cuiM oli' relay for opening' the circuit ol' said rst'- mentioned rclaywhcn said linf.J is calling or being called, means controlled by said cutolf relay for connecting said. line wipers wih said subscril'iers line.

23. In a telephone System, a subscriber-"1a line, a non-numerical trnnliing witch thai-cfor. trunk lines for talking purposes, will switch including liucl wipers always in ciw trica'l cngaganient wili one nl' said irunlr lines, a line relay in Said .mi l .'lfvnnj'ally conncctvil with flic subscril lin@rv auto matic lucana for progre` Vivclj/ n'iming; will switch upon cncl'gizatiori al alla lino automatic n'icans for sliopping ,siifl fswi'll; Without l'nrtlwr action on ilu pari; :fl las linc i'L-lay. a cubol'l relay. umm sfnznz'ollci by said cut-ill relay for ull rclay wlnn mill line is callcxl, means controlled in' v for connecing said lira vipera 'Y sullscribcs line ln a telephone systsfn'f. a nonWA4 tran "lng savicli. trunk lin( for tai; i j i po l s leading tliewli'rnnl. :raul swiclx man@ ing liuc u'ipcx's aln'ayzvI in alcol cui cumplo moin willi on@ (if will trunk line,Y low za ing line i'clay for w'nilrollihg l ol mail! svfil'cli. autoniaic :non im* pin# 1ra sivuly naming said :Wi :li Ppm; @new zation of tllo linc relay, auoin mean or stopping said switch witliols fui'llnfr afiox: on the part of the line relay. a cavoli? insana ccntmllcd oy said iufll relay or opening thc circuit nf said liuc relai-n n controllcrl by aan! lin@ rclay for control j the @Xtcn of opi-ration of said cutoff relay,

25. In a tclvplioncsystem, a non-ninnorical trunliing switch. trunk lines for la llliing pur poses leading therefrom, a line,` relay con trollingl the operation of salti Snitch` aut@ matic insana for progressiwly moving ,will switch upon thc cncrglzatiou nl die lire rclay.` automatic means i'oi' Hopping said Switch Without ful-ther action on par of tlm linc l'clay1 a. cutoff inlay for c'mlrollu 'g the circuit of Saul lino rclay means: con trollcil lry said line relay for nuealiani illy controlling the extent of operation of :faul cutoff relay.

'26. In a telephone system, a noxrnurnoricar trunliirngr witch, trunk lines for talking purA poses loadingr therefrom, said switch having; line wiperl always in electrical engagcincul with one of Sail trunk lines, a line relay cow trolling thc operation of said switch. aulou matic means for progressively mowing faul switch upon cnergization of the line rclay` automatic means for stopping said swcll without further action on the part of tlm line relay, ay cut-of relay, mcans controllml by said cutoff relay for opening the crcui of said lin?. relay, nml for amending c i tion to :mill trunk linac said lim velay loi' liu-cli the ifm-cnr', ol

271 ln a talc 15 tzrnnlzingj am poses wenn i trolling willfan invia ,line relay cuit or' mi ufl lint* 1",

for" i clr'tA .Carel cobol? relay curo?? Iic lim ula) lilo finned. relay inopei'utivo t0 close, its front Signed by me at Chicago, Cook mnnty, contacts, but pqrlnits it to open its back con Illinois, this 17th day 0f August, 1911.

tunis, anltonmtic nneuns for progressively A VILl 1% F. AMB. moving wml switclx upon the energizntimi of l j L l ,5 the. said second relay, and nntomatlc means llf'itnesses:

for btopping' Suid switch without further ac- ARTHUR J. RAY,

tion on the part of the Said second relay. EDWARD D. FALES. 

